1. Field of the Invention
This invention relates to the field of processing exposed photographic film and more particularly to a method and apparatus for automatically withdrawing an exposed filmstrip from its cartridge, tensioning the withdrawn filmstrip during processing, and rewinding the processed filmstrip into the cartridge for further handling.
2. Description of the Prior Art
Several techniques are employed in processing exposed rolls of positive and negative photographic film on a commercial scale. In a continuous processing method, in a darkroom or enclosure, the exposed filmstrips are withdrawn and severed from the cartridges, spliced together with other exposed filmstrips and slowly drawn through successive developing, rinsing and fixing solutions until processing is complete.
In a further processing method, referred to as "dip and dunk", the exposed filmstrips are withdrawn and severed from the cartridges and clipped at one end to a rack. Weights are attached to the free ends of the filmstrips so that gravity operates to tension the filmstrips as they hang downward from the rack during immersion in the processing solutions. When all of the filmstrips have been attached to the rack and weighted, the rack is successively suspended over the tanks containing the developing, fixing and rinsing solutions and then lowered to lower the weighted filmstrips into each such solution.
The removal of the filmstrips from the cartridges and attachment to the racks, and the attachment of the free hanging weights, requires care and is time consuming. After processing is complete, the removal of the filmstrips from the rack, the weights from the free ends and the handling of the processed filmstrips also require labor.
After either type of processing is complete, in the case of negative film types, the filmstrips may be spliced together or separately drawn through the printing stations of printers in which the images in the frames are exposed onto positive print media from which prints are made. In the case of positive film, the filmstrip image frames may be cut apart and mounted as "slides". Eventually, negative filmstrips are typically cut into envelope sized segments so they can be provided to the consumer within a typical package containing the prints made from the negative images.
Recently, it has been recognized that there are certain advantages to retaining the negative filmstrip with its cartridge through processing and printing, particularly so that it can be protected between these operations and can be returned to the consumer rolled back into the cartridge for safekeeping. For example, European Patent Application 0 469 594 A2 and German OLS P40 38 661.9 both describe a photographic processing, printing and storage method using the dip and dunk processing method, and the spliced-together filmstrip printing method. For processing each filmstrip, these applications describe, in one embodiment, that the cartridge spool is rotated to advance the leading end out of the cartridge aperture, the leading end is automatically gripped, and the filmstrip is pulled out of the cartridge. In at least the '661 application, a weight is attached to the free end and the cartridge is attached to a dip and dunk conveyer so that gravity causes the filmstrip to hang downward as the conveyer moves the filmstrip from tank to tank until processing is complete. The weight is apparently removed, and the processed filmstrip is rewound into the cartridge or severed and spliced for printing. In other embodiments, the exposed filmstrip is severed from the cartridge and continuous processed and printed while the cartridge is retained in order to reattach the processed filmstrip to its spool and rewind it back in.
These processes are complex and do not address certain of the difficulties with the dip and dunk processing method described above.
Problems to be Solved by the Invention
In the dip and dunk processing method, it is generally desirable to increase efficiency and save space by processing a large number of filmstrips simultaneously. In high volume processing, it is desirable to automate the loading of a number of cartridges closely spaced side by side on a rack, while allowing the processing fluids to be circulated vigorously in the solution tank. The use of free hanging weights on the filmstrip free ends helps to maintain tension in the filmstrip, but circulation of the processing solution and swaying movement of the rack and elongated filmstrips may cause contact and entanglement of closely spaced filmstrips. It is thus desirable to insure that the filmstrips of neighboring cartridges are kept under tension and not allowed to contact one another during immersion and withdrawal into and from the successive solutions.